On Tue, Nov 21 2017 at  7:10am -0500,
Mike Snitzer [off-list ref] wrote:

On Mon, Nov 20 2017 at  8:35pm -0500,
Mike Snitzer [off-list ref] wrote:

quoted

On Mon, Nov 20 2017 at  7:34pm -0500,
NeilBrown [off-list ref] wrote:

quoted

Please see
   https://www.redhat.com/archives/dm-devel/2017-August/msg00310.html

I'll very likely pick these up for 4.16 shortly.  But hope to work
through complete removal of DM's use of BIOSET_NEED_RESCUER for 4.16 as
well.

quoted

quoted

and
   https://www.redhat.com/archives/dm-devel/2017-August/msg00315.html

This one [1] needs a lot of review and testing.  Particularly against this
test case that Mikulas created to reproduce the snapshot deadlock (same
deadlock that motivated commit dbba42d8):
https://www.redhat.com/archives/dm-devel/2017-January/msg00064.html

...

Short of that, how would you like to proceed?

quoted

quoted

That would then just leave bcache....  I find it a bit of a challenge to
reason about the code in bcache, but if we can remove
BIOSET_NEED_RESCUER from dm, that will be an extra incentive for me to learn :-)

I'm all for properly removing BIOSET_NEED_RESCUER from DM.

Should we work to make [1] (above) sure it fixes Mikulas' test case?

I'll set in on reviewing and playing with [1] now.

Decided it a better use of my time to review and then hopefully use the
block-core's bio splitting infrastructure in DM.  Been meaning to do
that for quite a while anyway.  This mail from you just made it all the
more clear that needs doing:
https://www.redhat.com/archives/dm-devel/2017-September/msg00098.html

So I will start here on this patch you proposed:
https://www.redhat.com/archives/dm-devel/2017-September/msg00091.html
(of note, this patch slipped through the cracks because I was recovering
from injury when it originally came through).

Once DM is using q->bio_split I'll come back to this patch (aka
"[1]") as a starting point for the follow-on work to remove DM's use of
BIOSET_NEED_RESCUER:
https://www.redhat.com/archives/dm-devel/2017-August/msg00315.html

Mike